This invention relates to a process for paraffin-olefin alkylation producing highly branched paraffins under strong acid catalyzed conditions and in the presence of adamantyl carboxylic and sulfonic acids as hydride transfer catalysts. The compounds are preferably surfactants in the acid system employed.
The alkylation of olefins with isobutane, which proceeds by the addition of carbonium ions to the olefins under strong acid conditions, is a well-known process for producing a wide variety of useful hydrocarbon materials and particularly, gasoline blending components. For example, 2,2,4-trimethylpentane is a common blending component which is used for octane improvement of motor gasoline and it can be produced by alkylating butenes with isobutane in sulfuric acid or liquid HF. An example of such an acid catalyzed reaction process is described in U.S. Pat. No. 3,231,633.
Hydrocarbon conversion processes employing novel Lewis acid systems are disclosed in U.S. Pat. No. 4,229,611 and U.S. Pat. No. 4,162,233, both assigned to Exxon Research and Engineering Company.
U.S. Pat. No. 3,671,598 describes a process for isomerizing saturated cyclic hydrocarbons under strong acid conditions in the presence of an adamantane hydrocarbon. However, no suggestion is made that the process might be effective in paraffin-olefin alkylation nor that other specifically substituted adamantanes, particularly those with carboxy or sulfoxy substituents, might be more effective in increasing the rate of paraffin-olefin alkylation.
U.S. Pat. Nos. 4,357,481; 4,357,484; 4,357,482; and 4,357,483 to George M. Kramer (issued Nov. 2, 1982, and assigned to Exxon Research and Engineering Company) disclose the use of adamantane hydrocarbons in paraffin-olefin alkylation and non-cyclic paraffin isomerization, and the use of amino alkyladamantanes in paraffin-olefin alkylation and non-cyclic paraffin isomerization, respectively, in which rates of reaction are substantially increased as compared to those obtained in the absence of the specifically disclosed adamantane. However, none of the patents disclose or suggest the use of carboxy- or sulfoxy-containing adamantanes as rate enhancing agents in alkylation or isomerization processes.
New methods for producing such alkylated paraffinic hydrocarbons, useful as octane improvement agents, are constantly being searched for in an effort to increase product quality and process efficiency. Improved processing should lower side reactions, leading to less catalyst consumption while increasing product quality (octane number), yield and reaction rate.